Regenerative heat exchangers



June 6, 1967 H. BRANDT ET AL 3,323,579

REG ENERAT IVE HEAT EXCHANGER S Filed July 7, 1965 4 Sheets-Sheet 1 jay-.7.

June 6, 1967 Filed July 7, 1965 H. BRANDT ET AL REGENERATIVE HEAT EXCHANGERS 4 Sheets-Sheet REGENEHATIVE HEAT EXCHANGERS Filed July 7, 1965 4 Sheets-Sheet 5,

June 6, 1967 Filed July 7, 1965 H. BRANDT E AL REGENERATIVE HEAT EXCHANGERS 4 Sheets-Sheet 4 United States Patent 3,323,579 REGENERATIVE HEAT EXCHANGERS Herbert Brandt, Rothemuhle uber Olpe, Westphalia, Germany, and Herbert Sandmann, Hubertusweg, Olpe,

Westphalia, Germany Filed July 7, 1965, Ser. No. 470,019 Claims priority, application Germany, July 17, 1964, A 46,611, Reg. No. (utility model) 1,902,545 5 Claims. (Cl. 165-4) This invention relates to regenerative heat exchangers of the kind in which a substantially cylindrical regenerative heat exchange member, hereinafter referred to asa regenerator, is disposed stationary within an outer casing which has gas inlet and gas outlet means at its ends or otherwise suitably locate-d whereby hot gas may be led to the regenerator and passed in an axial direction through passages in the regenerator so as to give up heat from the said hot gas to a mass of plates or tubes which form the passages. Also disposed within the casing, and at each axial end of the regenerator, are rotatable duct members provided with means to lead air to one of the said duct members and from the other said duct member after passing in an axial direction through the regenerator, the said duct members rotating co-axially in relation to the stationary regenerator and having openings which pass over the end surfaces of the regenerator during such rotation, the opening or openings in one of the two duct members being disposed in mirror-image relation to the opening or openings in the other duct member so that air may flow direct from one duct member, through part of the regenerator mass to pick up heat from said mass, and then into the other duct member.

Usually the said openings in the duct members are of sector shape, and there may be one or more such ope11- ings in each duct member.

It is desirable that the ends of the rotatable duct members which sweep over the ends of the stationary regenerator should do so in such manner that there is the minimum amount of leakage between the duct members and the enclosing casing, and usually this has been effected by sealing members, sometimes spring-pressed, disposed at the edges of said duct opening so as to be pressed into contact with the end surfaces of the regenerator. It also has been proposed that the shaft which passes axially through the stationary regenerator and is connected to the two rotatable duct members should be in two parts provided with axially movable means to allow the two duct members and their sealing members to be retained in sealing engagement with the end surfaces of the regenerator during all phases of heat expansion.

Such regenerative heat exchangers are referred to hereinafter as of the kind referred to.

The means for effecting and retaining a gas and air seal between the rotatable duct members and the end surfaces of the regenerator have comprised a sealing member at each rotatable duct for facial engagement with a regenerator end surface, a frame carrying the sealing member, a gas-tight flexible and resilient expansion joint device between the rotatable duct and the sealing member frame, swivelling joint means also between the rotatable duct and the sealing member frame, and spring means for urging the sealing member frame toward the regenerator.

The gas tight flexible and resilient expansion joint device has comprised steel sheets bent to a substantially U- shaped cross-section and having a thickness of approximately 0.5 mm. which is sealingly secured at its longitudinal edges, respectively, to a connecting flange on the rotatable duct and to the sealing member frame.

Although, in such an arrangement of the rotatable duct and the sealing member, the rotation of the sealing memher, substantially in synchronism with the rotatable duct, is effected through the swivelling joint means, without any of such rotating drive having to be effected through the resilient expansion joint device, such expansion joint device being intended solely to seal off the interior of the rotatable air duct from the chamber through which the flue gases flow and to flex so as to take part in any axial movement of the sealing member relative to the rotatable duct, nevertheless, by reason of the angular movement of the elements of the swivelling joint means and the said axial movement of the sealing member relative to the rotatable duct, there are some slight relative movements in a circumferential direction between the sealing member frame and the rotatable duct. Such relative circumferential movements impose tangential stresses upon the expansion joint device which could lead to damage of the device.

Such tangential stresses may be intensified, or be imposed upon the expansion joint device, by temperature differences between the expansion joint device and the means by which the device is secured to the rotatable duct and to the sealing member frame.

Also, the sealing member frame may be displaced a small amount, relative to the rotatable duct in a circumferential or lateral direction, by reason of any clearance existing in the central or axial guidance means of the sealing member frame.

Locally different strong pressure forces can also be applied to the sealing member frame by differing heat expansion if the central driving shaft for the rotatable duct is not disposed exactly vertical; pulling and vibration forces may act upon the expansion joint device and lead to damage thereto.

The object of the present invention is to provide improvements in the flexible and resilient expansion joint device whereby any tangential forces may be applied thereto without the said device being damaged.

According to this invention a regenerative heat exchanger comprising a casing, a hot gas inlet chamber at the bottom of said casing, a gas outlet chamber at the top of said casing, a stationary regenerator within said casing between said chambers, a mass of plates in said regenerator providing a multiplicity of axial passages therethrough, an outlet air duct one open end of which is disposed within said gas inlet chamber, an inlet air duct one open end of which is disposed within said gas outlet chamber, rotatable air duct members above and below said regenerator having necks disposed in rotatable air and gas tight engagement with the open ends of the inlet and outlet air ducts, each air duct member having duets with openings at their ends adjacent the upper and lower faces of said regenerator whereby air emitted from said inlet air duct passes through said regenerator into said outlet air duct, and sealing assemblies disposed around the peripheries of the openings of said air duct members comprising a sealing member, a frame attached to said sealing member, an expansion member between said air duct member and said frame, swivel joint means between said air duct member and frame for transmitting the rotational movement of said air duct members to said sealing member, and resilient means urging said frame from said air duct members toward said regenerator, is characterized in that said expansion member comprises two superimposed thin, flexible resilient elements of U- shape section, one of said elements being secured at one edge to the air duct member, the other of said elements being secured at one edge to the sealing member frame, the opposite edges of the two elements. being free, and other plate elements secured to the air duct member and to the sealing member frame in overlapping relation to the secured edge portions of the expansion member elements whereby to form pockets within which the free edge portions of expansion member elements are disposed freely slidable.

In the accompanying drawings:

FIG. 1 is a diagrammatic sectional elevation of a regenerative heat exchanger of the kind referred to;

FIG. 2 is an enlarged fragmentary sectional elevation of a sealing member, its frame, a rotatable air duct and other related elements, including a flexible and resilient expansion joint device of a kind known hitherto;

FIG. 3 is an elevation of the swivelling joint means, looking in the direction of the arrow III in FIG. 2;

FIG. 4 is a transverse sectional elevation of one form of a flexible and resilient expansion joint device accord ing to this invention;

FIG. 5 is a fragmentary sectional plan view of a modification of the device shown in FIG. 4; and

FIG. 6 is a transverse sectional elevation of a further modification of the device shown in FIG. 4.

Referring to FIG. 1, a casing 11 provides at its bottom end a chamber 12 into which hot gases, from a suitable source, are admitted by means not shown, and the casing also has at its upper end a chamber 13 from which the said gases, after giving up heat to the regenerator hereinafter referred to, are withdrawn by means not shown.

Between the chambers 12 and 13 there is a stationary cylindrical regenerator 14 which is provided with plates or tubes which provide a mass 15 which forms passages which are open at the ends of the regenerator. Thereby, the hot gas from the chamber 12 may flow through the mass 15, give up heat to the said mass, and then pass on, as cool gas, to the chamber 13.

Within the chamber 12, and co-axial with the regenerator 14, there is the open end 16 of an outlet air duct 17, whilst within the chamber 13 there is a similar open end 18 of an inlet air duct 19.

Below the regenerator 14 there is an air duct member 20 which has an axial neck 21 which is disposed in rotatable, air and gas tight, engagement with the end 16 of the air duct 17, and has ducts 22 and 23 which have sector-shaped openings 22a and 23a, respectively, at their upper ends near to the bottom end face of the regenerator 14.

Similarly, above the regenerator 14 there is an air duct member 24 which has an axial neck 25 which is disposed in rotatable, air and gas tight, engagement with the end 18 of the air duct 19, and has ducts 26 and 27 which have sector-shaped openings 26a and 27a, respectively, at their lower ends near to the upper end face of the regenerator 14.

The bottom openings 26a and 27a of the ducts 26 and 2 7 are opposed, in the axial direction of the regenerator, to the upper openings 22a and 23a of the ducts 22 and 23, respectively, that is, the openings 26a and 27a of the ducts 26 and 27 are disposed in mirror-image manner to the openings 22a and 23a of the ducts 22 and 23, so that air emitted from the ducts 26 and 27 will pass through the regenerator and into the ducts 22 and 23.

The two air duct members 211 and 24 are both secured to a driving shaft 23 which passes vertically through an axial opening 29 in the regenerator 14 to provide a rotation drive to the duct members in known manner.

It is desirable that there be no leakage of fluid between the air ducts 22, 23, 26, 27 and the gas chambers 12, 13 and for this purpose sealing assemblies 30 are disposed around the peripheries of the openings 22a, 23a, 26a and 27a of the ducts 22, 23, 26, 27. The sealing assembly applied to the air duct 23 is shown in detail in FIGS. 2 and 3.

A. flange 31 surrounds the upper opening 23a of the air duct 23, and a frame 32 coincides with the said flange. An expansion member 33, having a section of U shape, and made of comparatively thin flexible and resilient material, for example spring steel, is secured at its edges in a gas-tight manner by clamps 34 and packing strips 35 to the flange 31 and to the frame 32.

The frame 32 also has a metal sealing strip 36 secured to it by screw studs 37, and the said sealing strip slides, during rotation of the duct members, on the surfaces of a flange 38 on the regenerator 14 and on radial ribs of the regenerator. Rollers 39, mounted externally on the regenerator, project through the flange 38 to engage the sealing strip 36 and assist the sliding movement between the sealing strip 36 and the flange 38 and the ribs of the regenerator.

Bolts 40, spaced apart at suitable intervals around the sealing assembly, are screwed into the frame 32, and pass freely through the flange 31 on the air duct 23 and also through a second flange 41 on the air duct. Helical compression springs 43 are disposed around the bolt 40 and between the flange 41 and a cup member 45 on the bolt. Thus, the frame 32 together with the sealing strip 36 is constantly urged by the springs 43 towards the regenerator 14. Stop nuts 46 on the bolt abut the flange 41 in order to limit the movement of the bolt, and by adjustment of those nuts on the bolt it is possible to limit wear of the sealing strip 36 during an initial running-in period. The pressure of the springs 43 on the sealing strip 36 can be adjusted by rotating the screwed bolt 40 in the frame 32. Damper springs 42 are disposed between the flange 31 and other cup members 44 on the bolts.

The frame 32 and the air duct 23 also are connected to each other by swivelling connections 48 which comprise a rod 49 connected at its ends by ball-joints to brackets 50 and 51 secured, respectively, to the frame 32 and to the air duct 23.

The pressure of the springs 43 around the air ducts 22, 23 of the lower rotatable duct member 20 is adjusted so that the springs do not carry much more than the weight of the sealing frame 32 and sealing strip 36, and therefore the sealing strip 36 is in relatively light contact with co-acting sealing surfaces of the regenerator 14 and wear of the strip 36 can be limited, to a certain degree, by adjustment of the lock nuts 46. The main part of the necessary contact pressure is provided by the pressure difference between the air in the ducts 22, 23 and the gas in the chamber 12.

Such a construction provides a gas-tight seal between the stationary regenerator end surfaces and the rotating air ducts. The rotation movement of the air ducts is applied to the sealing strips 36 and the frames 32 therefor by the carrier swivelling devices 48 which enable the sealing frames 32 to move axially as well as rotationally. The bolts 40 which locate the springs 42, 43 do not carry the sealing frame 32 and therefore they are not subjected to bending or jamming. A simple sealing means is provided.

During the rotating movement of the air ducts and the associated parts, each expansion joint device 30 seals off the interior of the air duct from the flue gases in the external chamber 12 and produces a flexible and resilient connection between the air duct and its associated sealing frames 32.

The expansion joint devices 30 hereinbefore described can perform flexible and resilient movements in the axial direction without suffering any damage, if the legs of the U-shaped sheets 33 are sufficiently long and if the radius of the Ubend is sufliciently large.

However, on account of the swinging of the swivelling devices 48, the movements in the axial direction result also in small relative movements in the circumferential direction between the sealing frames 32 and the air ducts. Thereby additional tangential stresses are imposed upon the expansion joint device 30, which could lead to damage to such device. An intensification of these tangential stresses is furthermore produced on account of temperature differences between the expansion joint devices and the means connecting them to the air ducts and the sealing frames. The sealing frame 32 itself has a certain displacement possibility relative to the connecting flange 31 of the air duct by reason of the clearance existing in the central or axial guidance means of the sealing frame 32.

The improved expansion joint device according to the present invention is shown in FIG. 4. The U-shaped expansion member 61 consists of two superimposed thin sheet steel elements 62 and 63 disposed with one edge portion 64 of the element 62 secured to the flange 31 of the air duct whilst one edge portion 65 of the element 63 is secured to the sealing member frame 32. The other edge portion 66 of the element 62 lies freely upon the other element 63 near to the secured edge portion 65 of the element 63 and is itself overlapped by a strip 67 which also is secured to the sealing member frame 32; the element portion 65 together with the strip 67 form a pocket in which the edge portion 66 of the element 62 may slide freely. Similarly, the other edge portion 68 of the element 63 lies and may slide freely within a pocket formed by the secured edge portion 64 of the element 62 and an overlying strip 69 secured to the flange 31. Thereby, the two elements 62, 63 of the expansion member may slide freely relative to each other, each said element only being secured by one edge portion. Thus, any possible circumferential movement of the expansion joint device is taken up by the relatively sliding elements and there are no tangential stresses appplied thereto.

The expansion joint device may be further improved in the manner shown in FIG. 5. The device may be formed of a plurality of assemblies 61 of elements 62 and 63, which assemblies are spaced apart from each other, at 70, around the air duct. Within the space 70 there is disposed a narrow expansion joint assembly 71, formed in a similar manner to the device assemblies 61 by two superimposed elements 72 and 73, and having elements 74 and 75 secured thereto and extending laterally therefrom to form pockets into which the ends of the expansion joint device assemblies 61 extend and freely slide therein, the pockets providing what are substantially labyrinth seals. The longitudinal movability of the expansion joint device in a circumferential direction thereby is increased, and a sufficiently large circumferential movement of the sealing member frame relative to the air duct is possible without imposing tangential stresses on the expansion joint.

By forming the expansion joint in accordance with this invention it is possible to use thinner steel sheets of, for example, 0.3 mm. thickness, whilst the two superimposed sheets provide a device of 0.6 mm. thickness which is larger than the single 0.5 mm. thickness hitherto usually used. The expansion joint therefore, whilst being more substantial than hitherto, is not any stiffer but, on the contrary, is more flexible and resilient in the axial direction of the regenerator.

For protection against corroding gases and against humidity deposits when operating under dew point, a covering of the double steel sheet expansion joint device 61 with heat and corrosion resistant materials can be provided in a further improvement, shown in FIG. 6 at 76.

A thus protected expansion joint will mainly be used at the cold end of the air preheater, in order to prevent the corrosion of the expansion joint metal sheets by humidity deposits, when operating under dew point conditions. For this purpose the heat protecting covering 76 can be provided on the air side only (in FIG. 6 it is shown on the gas side) which prevents an extensive cooling down of the expansion joint metal sheets. The heat insulating material providing the covering need not have to be non-porous in such a case.

The corrosion protection covering can be provided on the gas side of the expansion joint device by a non-porous material, for example of asbestos-fibre or glass-fibre structure coated with suitable plastics material or other corrosion resistant material.

What we claim and desire to secure by Letters Patent is:

1. A regenerative heat exchanger comprising a casing, a hot gas inlet chamber at the bottom of said casing, a gas outlet chamber at the top of said casing, a stationary regenerator within said casing between said chambers, a mass of plates in said regenerator providing a multiplicity of axial passages therethrough, an outlet air duct one open end of which is disposed within said gas inlet chamber, an inlet air duct one open end of which is disposed within said gas outlet chamber, rotatable air duct members above and below said regenerator having necks disposed in rotatable air and gas tight engagement with the open ends of the inlet and outlet air ducts, each air duct member having ducts with openings at their ends adjacent the upper and lower faces of said regenerator whereby air emitted from said inlet air duct passes through said regenerator into said outlet air duct, and sealing assemblies disposed around the peripheries of the openings of said air duct members comprising a sealing member, a frame attached to said sealing member, an expansion member between said air duct member and said frame, swivel joint means between said air duct member and frame for transmitting the rotational movement of said air duct members to said sealing member, and resilient means urging said frame from said air duct members toward said regenerator, characterized in that said expansion member comprises two superimposed thin, flexible resilient elements of U-shape section, one of said elements being secured at one edge to the air duct member, the other of said elements being secured at one edge to the sealing member frame, the opposite edges of the two elements being free, and other plate elements secured to the air duct member and to the sealing member frame in overlapping relation to the secured edge portions of the expansion member elements whereby to form pockets within which the free edge portions of expansion member elements are disposed freely slidable.

2. A regenerative heat exchanger according to claim 1, wherein the expansion member is formed in at least two units disposed substantially in end to end relation, the adjacent ends of the units being displaceable relative to each other, longitudinally of the expansion member.

3. A regenerative heat exchanger, according to claim 2, wherein the adjacent ends of the expansion member units are spaced apart, the space thereby formed being occupied by a filler unit of substantially similar section as the expansion member, the filler unit having pockets extending from both ends longitudinally thereof to receive the adjacent ends of the expansion member units.

4. A regenerative heat exchanger, according to claim 1, wherein the expansion member is covered by 'a member formed of heat and corrosion resistant material.

5. A regenerative heat exchanger, according to claim 4, wherein the said covering member is formed of fibrous heat and corrosion resistant material and is coated with other corrosion resistant material.

References Cited UNITED STATES PATENTS ROBERT A. OLEARY, Primary Examiner.

A. W- DAVIS, As istant Examiner. 

1. A REGENERATIVE HEAT EXCHANGER COMPRISING A CASING, A HOT GAS INLET CHAMBER AT THE BOTTOM OF SAID CASING, A GAS OUTLET CHAMBER AT THE TOP OF SAID CASING, A STATIONARY REGENERATOR WITHIN SAID CASING BETWEEN SAID CHAMBERS, A MASS OF PLATES IN SAID REGENERATOR PROVIDING A MULTIPLICITY OF AXIAL PASSAGES THERETHROUGH, AN OUTLET AIR DUCT ONE OPEN END OF WHICH IS DISPOSED WITHIN SAID GAS INLET CHAMBER, AN INLET AIR DUCT ONE OPEN END OF WHICH IS DISPOSED WITHIN SAID GAS OUTLET CHAMBER, ROTATABLE AIR DUCT MEMBERS ABOVE AND BELOW SAID REGENERATOR HAVING NECKS DISPOSED IN ROTATABLE AIR AND GAS TIGHT ENGAGEMENT WITH THE OPEN ENDS OF THE INLET AND OUTLET AIR DUCTS, EACH AIR DUCT MEMBER HAVING DUCTS WITH OPENINGS AT THEIR ENDS ADJACENT THE UPPER AND LOWER FACES OF SAID REGENERATOR WHEREBY AIR EMITTED FROM SAID INLET AIR DUCT PASSES THROUGH SAID REGENERATOR INTO SAID OUTLET AIR DUCT, AND SEALING ASSEMBLIES DISPOSED AROUND THE PERIPHERIES OF THE OPENINGS OF SAID AIR DUCT MEMBERS COMPRISING A SEALING MEMBER, A FRAME ATTACHED TO SAID SEALING MEMBER, AN EXPANSION MEMBER BETWEEN SAID AIR DUCT MEMBER AND SAID FRAME, SWIVEL JOINT MEANS BETWEEN SAID AIR DUCT MEMBER AND FRAME FOR TRANSMITTING THE ROTATIONAL MOVEMENT OF SAID AIR DUCT MEMBERS TO SAID SEALING MEMBER, AND RESILIENT MEANS URGING SAID FRAME FROM SAID AIR DUCT MEMBERS TOWARD SAID REGENERATOR, CHARACTERIZED IN THAT SAID EXPANSION MEMBER COMPRISES TWO SUPERIMPOSED THIN, FLEXIBLE RESILIENT ELEMENTS OF U-SHAPE SECTION, ONE OF SAID ELEMENTS BEING SECURED AT ONE EDGE TO THE AIR DUCT MEMBER, THE OTHER OF SAID ELEMENTS BEING SECURED AT ONE EDGE TO THE SEALING MEMBER FRAME, THE OPPOSITE EDGES OF THE TWO ELEMENTS BEING FREE, AND OTHER PLATE ELEMENTS SECURED TO THE AIR DUCT MEMBER AND TO THE SEALING MEMBER FRAME IN OVERLAPPING RELATION TO THE SECURED EDGE PORTIONS OF THE EXPANSION MEMBER ELEMENTS WHEREBY TO FORM POCKETS WITHIN WHICH THE FREE EDGE PORTIONS OF EXPANSION MEMBER ELEMENTS ARE DISPOSED FREELY SLIDABLE. 